This invention relates to a lockset for operating a latch bolt retractor mounted in a door, and particularly to a motorized lock actuator for electrically locking and unlocking a mortise lockset. More particularly, this invention relates to a door-mounted mortise lockset having an outside door handle that can be locked against rotation using an electromechanical lock actuator mechanism mounted in the mortise lockset.
Mortise locksets are well known and usually include various internal linkages and mechanical mechanisms for connecting a door handle to a retractable latch bolt. For example, mortise locks are disclosed in U.S. Pat. Nos. 4,572,556 and 4,589,691. Typically, a mortise lockset includes a rectangular case that fits into a cavity cut into a wooden door (or provided in a hollow metal door). The rectangular case contains the retractable latch bolt and the latch bolt retraction mechanism as well as some other components. Turning the door handle on a closed door causes the retraction mechanism to retract the latch bolt into the mortise lockset case mounted in the closed door so that the door is free to swing on its hinges to an opened position.
A locking mechanism of some kind is usually mounted in the mortise lockset and operated to control locking and unlocking of the outside door handle. One type of locking mechanism is actuated using a key and another type of locking mechanism is actuated using a push-button assembly. The key-actuated locking mechanism usually includes a lock cylinder attached to the mortise lockset and arranged to provide a keyway on the side of the door so that a person standing outside a closed door can insert a key into the keyway and turn the key either to lock or unlock the mortise lockset. The button-actuated locking mechanism usually includes a pair of push buttons attached to the mortise lockset and mounted in the vertical edge of the door in a place near the door handle so that the buttons can be pushed manually as long as the door is opened either to lock or unlock the mortise lockset. It is common to see mortise locksets outfitted with both key-actuated and button-actuated locking mechanisms.
It is also known to use a motor with a mortise lockset to control locking and unlocking of the outside doorknob or handle. Typically, such motor-controlled locking mechanism replaces the conventional manual button-actuated locking mechanism and is used in parallel with a conventional key-actuated locking mechanism. See, for example, U.S. Pat. No. 3,529,454 to Fish, U.S. Pat. No. 3,656,347 to Ford et al., U.S. Pat. No. 3,733,861 to Lester, and U.S. Pat. No. 3,854,763 to Zawadzki et al., for descriptions of electromechanical locking mechanisms.
Conventional electrified or battery-operated mortise locksets could potentially fail to function properly as a result of several problems that affect the operation of the electrical and mechanical locking mechanisms in such mortise locksets. As a result, an improved motorized mortise lockset is needed. It would be desirable to have a motorized mortise lockset that includes adequate, positive deadlocking features to ensure that the lockset remains securely locked whenever it is exposed to severe vibrational attack. Consumers would appreciate an improved motorized mortise lockset that includes a reliable auxiliary mechanical override system for locking and unlocking the lockset when mechanisms in the lockset become misaligned or jammed. Consumers also desire a battery-operated motorized mortise lockset that is designed to minimize energy consumption so that battery life is extended and that is also designed to come apart and go back together easily so that the lockset can be serviced or modified easily by the consumer or service technicians.
Lever handles are often used on mortise locks to ensure that such locks are operable by persons who have difficulty operating a doorknob which can be turned only by tightly gripping the knob. One problem is that hoodlums often exert tremendous force on such a lever handle, for example, by hitting it with a hammer or turning it using a long pipe in an attempt to vibrate and break the locking mechanism contained in the mortise lockset. What is needed is an electromechanical locking mechanism suitable for use in a mortise lockset that is sturdy enough to survive a vibration attack on the lockset and is mounted inside a mortise lock case so as to be protected from exposure to the environment. It is generally recognized that there may be problems that could affect the operation of certain types of motorized mortise locksets in the field over extended periods of time. In part, these problems could occur in these mechanisms due to their tendencies to be somewhat sensitive to motor timing on/off variations.
In an attempt to reduce these timing sensitivities, some types of locksets may utilize motor control systems which can be programmed to purposely energize the motor for an extended period of time. Although this would tend to minimize timing sensitivity, it can adversely consume additional battery energy thereby draining the motor batteries prematurely. It is generally accepted that, it is undesirable for the customer to frequently replace the batteries.
In addition, motor timing problems may cause disfunction of the lockset which could cause an operator attempting to actuate the lockset electrically to pause and repeat this lock actuating process in an effort to actuate the lockset.
Furthermore, there may exist conditions with certain electrically motorized locksets which allow the motor to become temporarily stalled. This temporary stalling can cause unwanted damage to the motor mechanism and can also adversely affect battery life. Sensors are sometimes used in certain locksets in an attempt to prevent or minimize these timing/stalling conditions, however, they tend to further complicate the overall design which results in higher cost to the customer.
Also, there is always the problem of motor stalling caused by overdriving an electromechanical linkage should it encounter an unexpected obstruction and become bound up or jammed as it tries to move within the lockset between a door-unlocking position and door-locking position. For example, these conventional linkages can often become jammed if excessive torque is applied to the outside doorknob or handle manually by someone holding the outside knob or handle before and/or during the locking of the lockset using the electromechanical locking mechanism.
A motorized lock actuator able to move a locking lug or the like in a mortise lockset to lock or unlock a door handle without stalling or damaging the miniature lock actuator motor or impairing operation of the lockset would be a welcomed improvement. Moreover, mortise locksets could be improved by providing a motorized lock actuator having a compact size and simple construction and a configuration designed to fit inside conventional mortise lockset cases. Such a design would make it possible for current owners of many conventional fully mechanical mortise locksets to retrofit such locksets with new motorized lock actuators in accordance with the present invention without a lot of trouble or expense.
According to the present invention, an improvement is provided for use in actuating a locking bar in a mortise lockset. The improvement includes means for moving the locking bar between door handle-locking and door handle-unlocking positions. The moving means includes a pivot hub having a pivot axis, a spring mounted on the pivot hub, and means for rotating the pivot hub about the pivot axis in either a clockwise or counterclockwise direction. To lock the mortise lockset, the pivot hub is rotated in a first "locking" direction by the rotating means to urge the spring into engagement with a first surface on the locking bar to move the locking bar to its door handle-locking position. Alternatively, to unlock the mortise lockset, the pivot hub is rotated in a second "unlocking" direction by the rotating means to urge the spring into engagement with a second surface on the locking bar to move the locking bar to its door handle-unlocking position.
In preferred embodiments, the rotating means includes an electric motor mounted in the lockset and a rotatable drive shaft driven by the motor. A slip-clutch mechanism joins the rotatable drive shaft to the pivot hub and normally functions to rotate the pivot hub about the pivot axis in response to rotation of the drive shaft by the motor. Illustratively, the drive shaft extends through an aperture formed in the pivot hub and the slip-clutch mechanism is retained in an internal chamber formed in the pivot hub.
Illustratively, the spring includes a base mounted on the pivot hub and a flexible cantilevered body extending away from the pivot hub and into an aperture formed in the locking bar. The cantilevered body of the spring includes a pair of cam surfaces that are positioned to lie in the locking bar aperture and sized to be movable in the aperture to reach and engage either the first or second surface on the locking bar during rotation of the pivot hub about its pivot axis. A "leading" cam surface is appended to the distal end of the cantilevered body and arranged to engage the first surface on the locking bar during rotation of the pivot hub in the first direction to move the locking bar to its door handle-locking position. A "trailing" cam surface is appended to the leading cam surface and arranged to engage the second surface on the locking bar during rotation of the pivot hub in the opposite second direction to move the locking bar to its door handle-unlocking position.
In use, the motor is used to rotate the pivot hub and spring in the first direction so as to advance the locking bar to its door handle-locking position due to camming engagement between the spring and the locking bar. One unique aspect of the invention is that the spring will behave as a fairly stiff member and move the locking bar to its door handle-locking position in response to motor-driven rotation of the pivot hub in the first direction. However, the spring is designed to be flexed between the locking bar and the pivot hub whenever an obstruction blocks movement of the locking bar in a locking direction and the motor continues to move the pivot hub and the spring. This flexure causes potential energy to be stored in the spring. Upon removal of the obstruction, the spring is designed to release and move the now freely movable locking bar to its handle-locking position. The spring also flexes and releases in the foregoing manner if movement of the locking bar is obstructed during use of the motor to move the locking bar in an unlocking direction to a door handle-unlocking position.
Advantageously, obstruction of the locking bar is not expected to hinder movement of the pivot hub or impair operation of the motor or lockset. The motor always rotates the pivot hub to a home position in either the locking or unlocking direction every time the motor is actuated. This is possible because the spring flexes relative to the pivot hub if movement of the locking bar is obstructed during motor-driven rotation of the pivot hub. Therefore, stalling of or damage to the motor and impairment of the operation of the lockset is minimized because of the novel way in which a spring is used to move the locking bar as the motor rotates the pivot hub between handle-locking and handle-unlocking positions. Thus, the spring functions as part of a reliable mechanical override system that is designed to provide a positive method of engaging and disengaging locking parts during misalignment or jamming conditions.
The slip-clutch mechanism eliminates the need for precise energized timing of the motor, thereby reducing the overall sensitivity of the motorized mortise lockset. Further, the slip-clutch mechanism is designed to provide low energy-consuming torque and is extremely resistant to frictional wear for maximum life.
The motors rotating pivot hub, and spring in accordance with the present invention are easily mounted in certain conventional mortise locksets to permit such a lockset to be converted from a fully mechanical lock actuator to a motorized lock actuator in the field or in the shop. Most importantly, any obstruction of the locking bar as it moves in the mortise lockset between its door handle-locking and door handle-unlocking positions does not disrupt operation of the motor, rotation of the pivot hub, or operation of the spring. This lengthens the life of the motor and minimizes disfunction of the motorized lock actuator.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.